I just tried the following on a Samsung S6 - problem is that there are no Avenza maps for my region, but the application tells me 'outside of map'. So the position is fine. Plus if I want to download a map it starts at the correct (my current) location.

In addition to Nico's comment, I would like to highlight that the Samsung Galaxy Tab S2 family (released 2015) are old-ish devices, and due to their relatively low specifications and relatively high power consumption, we don't recommend their use with Catalyst. The engine may still run, but it is likely that you will see performance issues (or in the worst case, the engine will stop tracking) when the device is stressed with a heavy workload. For example, if your field application (Avenza) is also processor intensive, this will limit the computing resources available to background processes (like Catalyst). Trimble maintains a list of the thoroughly tested devices based on what we see our users doing, and based on our qualification tests the Tab S2 is in the not 'supported' list. To check our minimum device specification requirements and a list of Trimble recommended devices, check here: Trimble Catalyst | Compatible Devices.

Did you grant the app permission to access location? (Check under app settings > permission)

Did you turn on the Android 'Location' feature and set it to use GPS from the phone? (The battery saving mode only uses WiFi for location)

It may help to play around with the settings under Avenva Map. i would suggest try disable 'Only Use Satellite Fixes' and 'Ignore Suspicious Fixes'. and experiment using 'Keep all Fixes' for other options.